Excellent ferroelectric properties of stoichiometric and Sr-deficient Sr2Bi4Ti5O18 thin films prepared by sol-gel process

Sr2Bi4Ti5O18 (SBTi) and Sr-deficient SBTi thin films were deposited on Pt/Ti/SiO2/Si(100) substrates using a sol-gel method. Structure, morphology and electric properties were investigated systematically. These films were random-oriented and were composed of rod-like grains. The remanent polarization (2P(r)) and coercive field (E-c) of SBTi films were 24 mu C/cm(2) and 68 kV/cm, respectively. This value of 2Pr was much higher than the reported value of SBTi prepared by pulse laser deposition. The compounds with Sr-deficient and Bi-excess composition showed a very large remanent polarization of 35.5 mu C/cm(2). More importantly, both films showed high fatigue resistance against continuous switching up to 3 x 10(10) cycles and excellent charge-retaining ability up to 3 x 10(4) s.